okay so not sure why you haven't been told to do this yet XD LOL right click your DayZ in steam library and go to properties then local files then verify integrity of local files. you'll probably be missing up to like 100 thats what happened with me and can now work i was missing 166 guess the last update didnt update properly and got corrupted XD lol but w/e.....but yeah do that and play sorry you havnt been able to play in so long. if that DOESN'T work make sure to run steam as admin and try to play it if that doesn't work verify files again while running steam as admin